The mechanisms that underlie the orderly sequential changes in gene expression during neurogenesis are unknown. Establishment of form and pattern within the nervous system is dependent on cellular interactions that are initiated early in development. These communications regulate cell proliferation, differentiation, neuroblast migration, axonal growth and guidance, target recognition, and ultimately synapse formation. The molecular machinery that relays this positional information is the foundation upon which neuronal diversity and function is based. How the nervous system is "wired" during embryogenesis remains a fundamental issue in molecular biology today. We have initiated our search for novel genes involved in these processes by identifying and characterizing genes involved in the neurogenesis of the fruit fly, Drosophila melanogaster. The fly was selected because of its relatively simple nervous system, availability of developmental mutants, and the possibility of genetic analysis of function. Thus far, we have identified three candidate genes and are focusing our efforts on two that are expressed in the central nervous system during development. These genes and the other candidates were identified by the enhancer detection method of transposon tagging in transgenic flies. Our goal is to use the knowledge gained from the molecular analysis of these genes to build the appropriate tools to search for mammalian genes that carry out related functions.